1. Technical Field
This disclosure relates to electronic sampling systems and to reducing signal distortions in such systems.
2. Description of Related Art
Electronic sampling systems have a wide range of applications, such as in MP3 players, DVD players, cellular telephones, data acquisition systems, test and measurement systems, and control systems. Electronic sampling systems may be found in a wide variety of sub-systems, such as analog-to-digital converters, switched capacitor networks, signal acquisition circuitry, and comparators.
Electronic sampling systems may employ sample and hold circuits that sample a voltage and maintain it in a storage device so that another circuit can measure or otherwise observe the acquired voltage. However, the mere act of sampling a signal of interest can cause distortion of the sampled signal and, in turn, in its sampling. This distortion can limit the useful voltage and/or frequency range of the input signal to be sampled.
This distortion may be produced by various factors, such as non-linear resistance characteristics of one or more switches in the sample and hold circuits, effects associated with turnoff thresholds, bulk effect, switch ratio match variations, and process variations. Distortion may also be produced by parasitic capacitances of switches in the sampling circuits, signal dependent charge injection by switches in the sampling circuits, and/or non-linear load currents flowing through input source resistances.
Efforts have been made to reduce such distortion, such as are described in U.S. Pat. No. 8,482, 442, entitled “System and Methods to Improve the Performance of Semiconductor Based Sampling System,” issued Jul. 9, 2013. However, these approaches can still result in distortion.